Hydrocarbon resid processing and visbreaking steam cracker feed

ABSTRACT

The invention concerns integration of hydroprocessing and steam cracking. A feed comprising crude or resid-containing fraction thereof is treated by hydroprocessing and visbreaking and then passed to a steam cracker to obtain a product comprising olefins.

RELATED APPLICATIONS

This application claims benefit of and priority to U.S. provisionalpatent application Ser. No. 60/728,640 (2005B125), filed Oct. 20, 2005,and also claims benefit of U.S. provisional patent application No.60/813,555 (2006B101), filed Jun. 14, 2006.

FIELD OF THE INVENTION

The invention relates to a method of making olefins from a crude orresid-containing fraction thereof.

BACKGROUND OF THE INVENTION

Thermal cracking of hydrocarbons is a petrochemical process that iswidely used to produce olefins such as ethylene, propylene, butylenes,butadiene, and aromatics such as benzene, toluene, and xylenes. Each ofthese is a valuable commercial product. For instance, the light olefinscan be oligomerized (e.g., to form lubricant basestocks), polymerized(e.g., to form polyethylene, polypropylene, and other plastics), and/orfunctionalized (e.g., to form acids, alcohols, aldehydes, and the like),all of which have well-known intermediate and/or end uses. One thermalcracking process is steam cracking, which involves cracking hydrocarbonsin the presence of hydrogen and/or hydrogen-containing components, suchas steam.

The starting feedstock for a conventional olefin production plant, asdescribed above, has been subjected to substantial (and expensive)processing before it reaches the olefin plant. Normally, whole crude isfirst subjected to desalting prior to being distilled or otherwisefractionated or cracked into a plurality of parts (fractions) such asgasoline, kerosene, naphtha, gas oil (vacuum or atmospheric) and thelike, including a high boiling residuum (“resid”). The resid cuttypically has a boiling point of greater than about 650° F. (343° C.),at about atmospheric pressure. After desalting and removal of the residfractions, conventionally, any of these fractions other than the 650°F.+ (343° C.+) resid, may be passed to a steam cracker or olefinproduction plant as the feedstock for that plant.

Typically in steam cracking, a hydrocarbon feedstock for steam cracking,such as naphtha, gas oil, or other non-resid containing fractions ofwhole crude oil, which may be obtained, for instance, by distilling orotherwise fractionating whole crude oil, is introduced to a steamcracker, usually mixed with steam. Conventional steam cracking utilizesa pyrolysis furnace that generally has two main sections: a convectionsection and a radiant section. In the conventional pyrolysis furnace,the hydrocarbon feedstock enters the less severe convection section ofthe furnace as a liquid (except for light feedstocks which enter as avapor) wherein it is heated and vaporized by indirect contact with hotflue gas from the radiant section and optionally by direct contact withsteam. The vaporized feedstock and steam mixture (if present) is thenintroduced through crossover piping into the radiant section where it isquickly heated, at pressures typically ranging from about 10 to about 30psig, to a severe hydrocarbon cracking temperature, such as in the rangeof from about 1450° F. (788° C.) to about 1550° F. (843° C.), to providethorough thermal cracking of the feedstream. The resulting products,comprising olefins, leave the pyrolysis furnace for further downstreamseparation and processing.

After cracking, the effluent from the pyrolysis furnace contains gaseoushydrocarbons of great variety, e.g., saturated, monounsaturated, andpolyunsaturated, and can be aliphatic and/or aromatic, as well assignificant amounts of molecular hydrogen. The cracked product is thenfurther processed such as in the olefin production plant to produce, asproducts of the plant, the various separate streams of high purityproducts mentioned above, i.e., hydrogen, the light olefins ethylene,propylene, and butenes, and aromatic compounds, as well as otherproducts such as pyrolysis gasoline.

As worldwide demand for light olefins increases and the availability offavorable crude sources is depleted, it becomes necessary to utilizeheavier crudes (i.e., those having higher proportions of resid), whichrequires increased capital investments to process and handle therefining byproducts and purchase the higher grade feedstocks. It ishighly desirable to have processes that can take lower cost, heaviercrudes, and produce a more favorable product mix of light olefins, moreefficiently.

It has previously been proposed to upgrade certain crude fractions,prior to steam cracking, by first hydroprocessing the feed. Forinstance, U.S. Pat. Nos. 3,855,113 and 6,190,533 are directed to aprocess comprising passing the feed to a hydroprocessing zone followedby a steam cracking zone. In neither case, however, is whole crude or afraction comprising resid passed directly to the hydroprocessing zone.See also GB 2071133 and Erdoel & Kohle, Erdgas, Petrochemie (1981),34(1), 443-6.

Conventional resid hydroprocessing or “residfining” is a known processfor upgrading a portion of the resid containing crude fraction. Thehydrogenated liquid and vapor products (but not the resid products) fromresidfining are typically fractionated into more valuable streams, e.g.,fuel oil, diesel, heating oil, jet, kerosene, gasoline, LPG, and fuelgas. Each of these is useful per se as fuels and/or as intermediates forthe production of, for instance, petrochemicals. By way of example, fueloil may also be cracked to produce the lighter boiling fuels, such asgasoline, LPG, and fuel gas and/or the petrochemicals ethylene,propylene, and butanes. The resid fraction is typically a low-valueproduct. However, subsequent to hydroprocessing and before or during thefurther distillation of the resid stream, conversion, deasphalting, orother processing may be performed on the resid containing crudefraction.

U.S. Pat. No. 3,898,299 discloses a-process for removing the residfractions and producing olefins from the non-resid, lower boiling pointhydrocarbons. Atmospheric resid from distillation is hydroprocessed andthe liquid hydroprocessor effluent is “fed in the presence of steamdirectly to the pyrolysis zone wherein unvapourized feedstock is removedas a residue fraction in a separation zone prior to entry of thevapourised distillate fraction into that region of the pyrolysis zonemaintained under conditions which effect thermal cracking.” However, the'299 reference only teaches conventional hydroprocessing and thermalsteam cracking of the non-resid-containing overhead stream and does notproperly suggest or teach how to use the resid containing effluent froma resid hydroprocessing unit as a feed for a steam cracker. The '299patent requires the typical separation and removal of the 650° F.+ (343°C.) boiling point fractions from the treated hydroprocessor effluent,prior to steam cracking. Only the distillate fractions are processed toolefins. Those skilled in the art are well aware of the practicaldifficulties involving equipment fouling of conventional equipment ofthe '299 patent, for steam cracking resid-containing feeds. Residhydroprocessing is a known process for upgrading resid to fuels such asfuel oil, diesel, heating oil, jet, kerosene, gasoline, LPG, and fuelgas. Each of these are useful as fuels and/or as intermediates for theproduction of, for instance, petrochemicals.

Other patents of interest related to cracking heavy feeds include U.S.Pat. No. 4,257,871, to Wemicke; U.S. Pat. No. 4,065,379, to Soonawala;U.S. Pat. No. 4,180,453, to Franck; and U.S. Pat. No. 4,210,520, toWernicke. However, each of the aforementioned patents do not adequatelyteach how to steam crack a resid-containing hydrocarbon stream for theproduction of olefins.

In U.S. Pat. No. 4,257,871, vacuum resid is used for the production ofolefins by first separating the asphalt therein, blending resultantasphalt-depleted fraction with a lighter fraction, and then subjectingthe blend to a conventional catalytic hydrogenation step prior tothermal cracking. See also U.S. Pat. No. 4,297,204.

Japanese Kokai Patent Application Sho 58[1983]-98387 relates to a methodof manufacture of gaseous olefin and mononuclear aromatic hydrocarbon,characterized by hydrogenating crude with hydrogen and a hydrogenationcatalyst, followed by thermal cracking. In an embodiment hydrogenatedcrude oil may be distilled or flashed to separate components with theoverhead stream fed to the thermal cracking process. See also JapaneseKokai Patent Application Sho 58[1983]-005393 and Japanese Kokai PatentApplication Sho 57[1982]-212294.

U.S. Pat. No. 6,303,842 teaches producing olefins by thermally steamcracking residuum containing a short residuum having a boiling pointrange greater than 565° C., wherein at least 3 weight percent of theshort residuum has a boiling point greater than or equal to 650° C. Thefeedstock is produced by conventional hydroprocessing. Other referencesof interest include U.S. Pat. Nos. 3,855,113; 4,057,490; 4,179,355; and6,743,961. Still other patents of interest related to cracking heavyfeeds include U.S. Pat. No. 4,257,871, to Wemicke; U.S. Pat. No.4,065,379, to Soonawala; U.S. Pat. No. 4,180,453, to Franck; and U.S.Pat. No. 4,210,520, to Wernicke.

WO 2004/005431 discloses a process for steam cracking certain feedstockscomprising resid, whereby a substantial unconverted liquid residfraction is removed prior to steam cracking. The '5431 invention doesnot disclose or teach hydrogenation as a process useful for upgradingheavy, sour, crude oil and resid feedstocks, including the residfractions, such that the whole crude, including resid fractions, may besteam cracked and converted to petrochemicals. Heavy, sour feedstocks donot contain high concentrations of the linear paraffins, which are knownto make the highest quality steam cracker feedstocks. The atmosphericand vacuum resid fractions of crude oils containing >2.0 wt % sulfuralmost always have a hydrogen content <12.5 wt % and typically they havea hydrogen content of <11.0 wt %. It is well known that conventionalresid hydroprocessing produces product highly prone to fouling.

There remains in the art, means and processes for economical processingof heavy, resid containing whole crudes, and resid containinghydrocarbon fractions thereof, for the production of olefins, aromatics,and other valuable petrochemical products. All known art previous tothis invention, has deficiencies, shortcomings, or undesirable aspects.

SUMMARY OF THE INVENTION

The present inventors have surprisingly discovered that residhydroprocessing that is increased in severity and heat integrated with asteam cracker, may be used to produce useful products such as olefinsand/or aromatic compounds by integration of at least one hydroprocessingstep, at least one step of visbreaking, and at least one thermalcracking step.

This invention provides a process by which a hydroprocessing effluentcontaining a resid fraction therein may be used as steam cracker feed.The inventors have also discovered that crude or a resid-containingfraction thereof may be hydroprocessed for use as steam cracker feedstock. The hydroprocessed, resid-containing feedstock may be steamcracked to produce useful products such as olefins and/or aromaticcompounds. The invention is directed to a process integratinghydrogenation of a resid-containing material with steam cracking toobtain an olefins product.

In an embodiment, there is a process of producing olefins from afeedstream comprising crude or crude fractions containing resid, theprocess including a step of hydroprocessing, a step of visbreaking, anda step of thermal cracking. The process and apparatus are capable ofrejecting only the heaviest, most undesirable resid components of thefeedstream and passing substantially only vaporized components,including vaporized components derived from resid, into the radiantsection of the steam cracker.

In preferred embodiments of any of the aforementioned, there is a stepof visbreaking prior to steam cracking and/or there is a vapor liquidseparation device, e.g., a visbreaker, integrated with the thermalpyrolysis furnace. Visbreaking can occur in the integrated vapor liquidseparation device eliminating the need for a separate conventionalvisbreaker process or equipment.

In another preferred embodiment, there is a process comprising crackinga portion of the resid components in a hydroprocessing step, obtainingan effluent from a resid hydroprocessing unit, visbreaking the effluent,and passing the overhead from the visbreaking step to the radiantsection of a steam cracker. Here again the visbreaking may occur in anintegrated vapor liquid separation device or a visbreaker separate fromthe steam cracker.

In one preferred embodiment, the process further comprises an integratedfractionation step, such as by use of a flash drum to remove asphaltenesand/or remaining fractions boiling above about 1050° F. (about 566° C.)and preferably only those remaining fractions boiling above about 1100°F. (about 593° C.) from the feed prior to passing the feed to theradiant section of the steam cracker unit. Surprisingly, this can beaccomplished with fouling rates that are equal to or better than thefouling rates of VGO steam cracker feedstocks. Preferably at least oneflash drum or other flash device, such as an in-line choke, or orificeplate is provided to reduce the pressure in the hydroprocessor effluentand cause the conversion of some of the liquids to vapors, is provided.Preferably the flashing device is integrated with the feed to the steamcracker thermal pyrolysis unit. Integrated means heat integrated, suchthat heat may be obtained for the conversion, cracking, flashing, andseparation process from one or more of the steps in the process, such asduring hydroprocessing, preheating in a convection section, and/or fromthe steam cracker. In preferred embodiments, the pressure of theeffluent form the hydroprocessor is flashed or depressurized, at leastone of prior to separation or during separation. Flashing also includesthe possibility of introducing the effluent to a vacuum.

In another preferred embodiment, the invention comprises a process forpreparing a resid-containing hydrocarbon feedstock for steam crackingthe same. The inventive process comprises in one aspect hydroprocessingthe feed to hydrogenate the feedstock to improve the hydrogen saturationof the cracked effluent. The inventive process further comprisesimproving the hydrogenated resid-containing hydroprocessor effluent byfurther processing the same in a visbreaker to thermally crack theundesirable effluent and recover an improved resid containing vaporeffluent from the visbreaking process in a vapor liquid separator, suchas may be used in a visbreaking separation process. The inventioncomprises still further improving the quality of the feed by visbreakingand/or separating the visbreak-processed material in a visbreaker and/orvapor-liquid separator that is integrated with the steam cracker, morepreferably with the convection section of the steam cracker.

In an embodiment of the various embodiments of the invention wherein theeffluent is obtained from a resid hydroprocessing unit, the feedstreamto the resid hydroprocessing unit comprises crude that has not beenfractionated or a crude fraction containing resid. In anotherembodiment, hydroprocessing is carried out using at least one fixed bedhydrogenation reactor, ebullating reactor, or fluidized hydrogenationreactors, prior to being fed to a thermal pyrolysis unit.

In yet other embodiments, feeds to be hydroprocessed comprise one ormore of recycled steam cracker tar, heavy crudes, or topped crude, andfeeds to be steam cracked comprise hydroprocessed recycled steam crackertar, heavy crudes, or topped crudes. In another preferred embodiment,the source of hydrogen for the hydroprocessing is from remote methane.

Some preferred embodiments also include combinations of two or more ofthe above embodiments, including preferred embodiments. In yet stillanother preferred embodiment, feeds such as whole crude, with or withoutdesalting, or the product of a refinery pipestill or a chemicalintermediate stream containing asphaltene or resid, such as atmosphericresid or vacuum resid, or steam cracked tar are hydroprocessed usingfixed bed hydrogenation reactors or ebullating or fluidizedhydrogenation reactors prior to being fed to a thermal pyrolysis unithaving a vapor liquid separation device integrated therewith.

The invention is also directed to a system comprising a hydroprocessingapparatus, a thermal pyrolysis unit, and at least one vapor liquidseparation device for visbreaking, wherein the vapor liquid separationdevice is advantageously integrated with the thermal pyrolysis unit, andalso to a process comprising feeding a resid-containing feed through thesystem to obtain a product comprising light olefins (one or more ofC2-C6 olefins). In a preferred embodiment, the system further comprisesa steam reformer for converting methane to hydrogen to provide hydrogento the hydroprocessing apparatus. It is an object of the invention toprovide resid as a preferred feed to the olefins producer, and thusenable use of lower quality crude feedstocks. It is another object ofthe invention to increase the hydrogen content of steam cracker feedwhile minimizing the increase in hydrogen content of the resid contentof the feed.

These and other objects, features, and advantages will become apparentas reference is made to the following detailed description, preferredembodiments, examples, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, reference numerals, labels, or otherindicia identifying parts or process components, are used to denote likeparts or components, throughout the several views.

FIGS. 1-6 are process flow diagrams illustrating some exemplaryembodiments of the invention.

DETAILED DESCRIPTION

In one embodiment, the resid-containing, incipient thermally crackedeffluent from a hydroprocessor, preferably a resid hydroprocessor,including those resid fractions having a boiling point of less thanabout 1050° F. (about 566° C.) and preferably those resid fractionshaving a boiling point of less than about 1100° F. (about 593° C.), arefurther cracked substantially, such as in a visbreaker/separator, andused as feed for a steam cracker or other thermal pyrolysis unit. In thepyrolysis unit, the vaporized fractions are converted to desiredproducts including olefins. The terms thermal pyrolysis unit, pyrolysisunit, steam cracker, and steamcracker are used synonymously herein; allrefer to what is conventionally known as a steam cracker, even thoughsteam is optional.

According to the invention a crude or fraction thereof containing residis hydroprocessed. Typically, resid hydroprocessing according to thepresent invention may be carried out at a temperature of at least about600° F. (315° C.), preferably at least about 650° F. (343° C.), morepreferably at least about 750° F. (399° C.). Preferably the pressure isat least 1800 psig. The intention is to initiate thermal cracking of atleast a portion of the 650° F.+ (343° C.+) resid, e.g., incipientthermal cracking, during the hydroprocessing step. Such processing ofheavy crudes or heavy resid fractions may typically require atemperature of at least about 750° F. (399° C.+) to initiate thermalcracking of the lighter resid fractions. Thus, in some embodiments ofthe inventive processes, the incipient thermal cracking temperature forthe hydroprocessor unit will be at least about 750° F. (399° C.), or atleast about 780° F. (451° C.), and in still other embodiments, thetemperature will have to be at least about 800° F. (427° C.). Apreferred processing temperature range may be from about 650° F. (343°C.) to about 900° F. (482° C.). According to still other alternativeembodiments of the processes of the present invention, hydroprocessingmay be performed at a temperature of from about 500° F. (260° C.) toabout 900° F. (482° C.), preferably from about 650° F (343° C.) to 900°F. (482° C.), more preferably from about 700° F. (371° C.) to 900° F.(482° C.), more preferably from about 750° F. (399° C.) to about 900° F.(482° C.), and still more preferably from about 750° F. (399° C.) toabout 800° F. (427° C.). In some embodiments, the preferred pressure isfrom about 500 to 10,000 psig, preferably 1000 to 4000 psig may be used,and more preferably from about 1500 to 3000 psig. The selectedtemperature may vary according to the composition and conditions of thehydrocarbon feed. Preferred liquid hourly space velocity may be fromabout 0.1 to 5, preferably 0.25 to 1. The hydrogen supply rate (makeupand recycle hydrogen) to the hydroconversion zone may be in the range offrom about 500 to about 20,000 standard cubic feet per barrel ofhydrocarbon feed, preferably about 2,000 to 5,000 standard cubic feetper barrel. The hydroprocessing may be carried out utilizing a singlezone or a plurality of hydroprocessing zones, e.g., two or morehydroprocessing zones in parallel or in series. For example, in oneembodiment a first zone may comprise a first catalyst that may bedesigned to accumulate most of the metals removed from the feedstock,and in series a second zone may comprise a second catalyst that can bedesigned for maximum heteroatom removal and aromatics hydrogenation. Inanother embodiment, a first catalyst can be designed to accumulate mostof the metals removed from the feedstock, and a second zone with asecond catalyst can be designed for maximum heteroatom removal and athird zone with a third catalyst can be designed to increase aromaticshydrogenation. The first and second catalysts may be piped in seriesreactors or loaded in series in the same zone. Design specifics as itrelates to the resid hydroprocessor(s) alone do not form a critical partof this invention.

The catalyst employed in the typical commercial hydroconversion zone(s)is comprised of material having hydrogenation-dehydrogenation activitytogether with an amorphous carrier. Exemplary amorphous carriers includealumina, silica-alumina, silica, zirconia, or titania.Hydrogenation-dehydrogenation components of the catalyst preferablycomprise at least one hydrogenation component selected from Group VImetals and compounds of Group VI metals and at least one hydrogenationcomponent selected from Group VIII metals and compounds of Group VIIImetals. Preferred combinations of hydrogenation components includenickel sulfide with molybdenum sulfide, cobalt sulfide with molybdenumsulfide, cobalt with molybdenum, and nickel with tungsten. The catalystemployed in the invention may also be comprised of a material havinghydrogenation-dehydrogenation activity formulated without an amorphouscarrier. Exemplary catalysts include Nebula.

According to the present invention, resid hydroprocessing may preferablybe carried out at a temperature and pressure that is more severe thanconventional hydroprocessing processes. In one embodiment, thehydroprocessing preferably may be carried out at above 650° F. (343° C.)and up to a temperature that produces substantial hydrocarbon crackingduring the hydrogenation process, such as about 750° F. (399° C.) toabout 800° F. (427° C.). This not only generates a hydrogenated residcomponent but also cracks or breaks down a substantial portion of theresid component into light fractions. The light fractions, along withinjected steam, help with conversion, cracking and further vaporizationand thermal processing of the stream within the steam cracker, such aswithin the cracker piping.

Resid hydroprocessing includes substantially any process resulting inthe hydrogenation of resid and/or resid-containing fractions, andencompasses (but is not limited to) commercially available residhydroprocessing technologies. Examples of these commercially availableprocesses are the H-Oil process, the Chevron RDS, VRDS, OCR, andLC-Fining processes, the HYVAHL process, and the ENI-Snamprogetti ESTprocess. Suitable hydroprocessing processes may include, for example,fixed bed catalyst systems, ebullating bed systems, fluidized bedsystems, and/or combinations thereof. Hydroprocessing as used hereinalso includes some mild cracking of the 650° F.+ (343° C.+) residcomponent of the hydrocarbon feed, and preferably even some cracking ofthe boiling fractions from 650° F. (343° C.) up to the about 11 00° F.(593° C.) boiling point fractions, and more preferably the 650° F. up tothe about 900° F. (482° C.) fractions.

The hydrogenated feed from the hydroprocessor may then be furtherfractionated or vaporized and fed whole to a steam cracker.Substantially complete vaporization may take place in the steam crackersystem. A combination of separators, flash separators, and/or separationpots may be provided as desired between hydrogenation and cracking. Inpreferred embodiments, separator processes may be integrated with theheating and cracking process, such as with the steam cracker. e.g., Avapor-liquid separator or separation process may be provided within theconvection section of the steam cracker or between the convectionsection and radiant section of the cracker.

Resid hydroprocessing preferably comprises increasing the hydrogencontent of the whole crude or crude fraction containing resid, by atleast about 1 wt %, preferably by 1.5 wt %, and most preferably to anearly saturated or fuilly saturated feed stream effluent from thehydroprocessor. It may be preferred in some embodiments that theeffluent from the hydroprocessor has a hydrogen content in excess of12.5 wt % and more preferably in excess of 13 wt %. Increasing thehydrogen content of the whole crudes, crude fractions, or other feedstocks may serve to render the hydrogenated product thereof suitable forfeeding to a pyrolysis unit for cracking, thereby generating morevaluable end products, such as olefins. Thereby, lower cost steamcracker feeds may be used for the production of olefins. Suitable lowervalue feeds may typically include heavier crudes, those hydrocarbonfeedstocks that have high concentrations of resid, high sulfur, highTAN, high aromatics, and/or low hydrogen content. Hydrogenation of thecrude or crude fractions, and removal of contaminants may facilitatefeeding such effluent to a steam cracker system or apparatus that iscapable of rejecting the heaviest components of the feedstream, such asthe asphaltenes and the 1100° F.+ (593° C.+) fractions. The remainder ofthe effluent, including the vaporized resid fraction, e.g., the crackedand vaporized 650° F.+ (343° C.), up to the 1050° F.+ (565° C.)fractions, even up to the 1100° F.+ (593° C.+) fractions, up to andincluding some of the 1400° F. (760TC) and lower boiling point fractionsthat is vaporized, is fed into the radiant section of the steam crackerfor severe cracking and production of valuable petrochemical products,such as olefins, without undesirable fouling and without resulting inthe undesirable production of tar and coke.

Surprisingly, this process may be performed without resulting inuncontrollable equipment fouling or the undesirable production of highyields of tar and resid-containing byproducts. Also surprisingly, thefully hydrogenated crude may be substantially completely vaporized inthe steam cracker and result in increased petrochemical yields.Conversion and vaporization may also be supported by steam assistedflash vaporization. Further, the severe hydrogenation may also greatlyreduce production of steam cracker tar.

In a preferred embodiment, the hydroprocessor effluent selected to besteam cracked comprises a substantial fraction boiling from about 700°F. (371° C.) to about 900° F. (482° C.). In another preferredembodiment, if the hydroprocessor effluent contains resid, it may befirst treated to remove a portion of the resid, such as the asphaltenes,prior to feeding the treated and hydrogenated resid-containing materialinto the convection section or the radiant section of the thermalpyrolysis unit (steam cracker). Preferred methods of removing theundesirable resid portions are discussed below.

Crude, as used herein, means whole crude oil as it issues from awellhead, production field facility, transportation facility, or otherinitial field processing facility, optionally including crude that hasbeen processed by a step of desalting, treating, and/or other steps asmay be necessary to render it acceptable for conventional distillationin a refinery. Crude as used herein is presumed to contain resid unlessotherwise specified.

Crude fractions are typically obtained from the refinery pipestill.Although any crude fraction obtained from the refinery pipestill may beuseful in the present invention, the significant advantage offered bythe present invention is that crude or crude fractions still containingall or a portion of the original resid present in the whole crudeobtained from the wellhead may be hydroprocessed and subsequently usedas feed for a steam cracker. In one embodiment, the crude or otherfeedstock to the hydroprocessing unit may comprise at least about 1 wt %resid, preferably at least about 5 wt % resid, more preferably at leastabout 10 wt % resid, and even more preferably at least about 20 wt %resid.

Resid as used herein refers to the complex mixture of heavy petroleumcompounds otherwise known in the art as residuum or residual.Atmospheric resid is the bottoms product produced in atmosphericdistillation when the endpoint of the heaviest distilled product isnominally 650° F. (343° C.), and is referred to as 6500F+ (343° C.+)resid. Vacuum resid is the bottoms product from a column under vacuumwhen the heaviest distilled product is nominally 1050° F. (566° C.), andis referred to as 1050° F.+ (565° C.+) resid. (The term “nominally”means here that reasonable experts may disagree on the exact cut pointfor these terms, but probably by no more than ±50° F. (or at most ±100°F.). This 1050° F.+ (565° C.) portion contains asphaltenes, whichtraditionally are considered to be an anathema to the steam cracker,resulting in corrosion and fouling of the apparatus. The term “resid” asused herein means the 650° F.+ (343° C.+) resid and 1050° F.+ (565° C.+)resid unless otherwise specified; note that 650° F.+ (343° C. +) residcomprises 1050° F.+ (565° C.+) resid. According to this invention, atleast a portion of the 650° F.+ (343° C.) resid, up to at least the1050° F.+ (565° C.) boiling point fraction, is vaporized, such as during(i) hydroprocessing, (ii) when combined with steam, and/or (iii) whenthe pressure is reduced or flashed between the hydroprocessing unit andsteam cracking, e.g., during flash separation.

Resid may also typically contain a high proportion of undesirableimpurities such as sulfur and nitrogen, as well as high molecular weight(C12+) naphthenic acids (measured in terms of TAN according to ASTMD-664). Yet another advantage of the present invention is that feedshigh in one or more of these impurities may be readily processed. As anexample of one specific species of impurities, a large amount of sulfurmay be tied up in multi-ring heterocycles. By hydrotreating residcontaining such species, not only is sulfur removed as H₂S, but theheterocyclic rings are broken up to yield a significant amount ofmonocyclic aromatic species, which are often valuable commodities bythemselves and are also a preferred feed to steam crackers.

The term “hydroprocessing” as used herein is defined to include thoseprocesses comprising processing a hydrocarbon feed in the presence ofhydrogen to hydrogenate or otherwise cause hydrogen to react with atleast a portion of the feed. This includes, but is not limited to, aprocess comprising the step of heating a resid-containing hydrocarbonfeed stream in a hydroprocessing step in the presence of hydrogen,preferably also under pressure. Hydroprocessing may also include but isnot limited to the process known as, hydrofining, hydrotreating,hydrodesulfurization (HDS), hydrodenitrogenation (HDN),hydrodeoxygenation (HDO), hydrofining and hydrocracking.

The term “steam cracker” as used herein is also known more generally asthermal pyrolysis unit or furnace or just pyrolysis furnace. Steam,although optional, is typically added for one or more reasons, such asto reduce hydrocarbon partial pressure, to control residence time,and/or to minimize coke formation. In preferred embodiments the steammay be superheated, such as in the convection section of the pyrolysisunit, and/or the steam may be sour or treated process steam.

It is conventional to desalt prior to passing the feed to the pipestill.When resid from the pipestill is meant to be hydroprocessed, the crudeoil feed to the refinery is often double desalted. Desalting typicallyremoves metal salts such as NaCl. However, the desalted crude and crudefractions may still contain relatively high concentrations of one ormore impurities such as naphthenic acids, sulfur, and/or nitrogen.Another advantage of the present invention is that crude and crudefractions containing one or more of such naphthenic acid, sulfur, and/ornitrogen impurities may be readily processed.

In a preferred embodiment, wherein the feed, comprises crude oratmospheric resids that contain appreciable amounts of 1050° F.+ (565°C.+) resids, e.g., 10 wt % or more of resid, or 20 wt % or more ofresid, the resid-containing feed, after hydroprocessing, may be passedinto the convection section of a pyrolysis unit, where it is heated.Then the heated feed may be passed to a visbreaker or other vapor liquidseparation device to drop out the heaviest fraction (e.g., substantiallythe asphaltenes and 1050° F.+ (565° C.+) fractions). Preferably, suchdevice is heat integrated. Heat integration provides added efficiency tothe visbreaker or separator.

In addition to the incipient thermal cracking of the resid fractionsthat occurs during hydroprocessing, a significant portion of additionalcracking, conversion, and flash separation that occurs within thevisbreaker/separator. This further cracking and conversion is caused byapplying unconventionally high separating/visbreaking temperatures foran unconventionally short contact time, thereby minimizing orcontrolling coking to an acceptable level. When the resid-containingfeed is heated to less than about 650° F. (343° C.) and even up to onlyabout 700° F. in the convection section and the feed has a relativelyshort residence time in the liquid-vapor separation device, such as istypical with conventional resid hydrogenation processes, little to nothermal cracking may occur and generally only molecules that vaporize atthese conditions can be separated. e.g., generally non-resid typecomponents. However, when the resid-containing feed is heated to above700° F. (371° C.) as according to the present invention, preferablyabove 750° F. (399° F.), still more preferably above 780° F. (415° C.)in the convection section and has a longer residence time in theliquid-vapor separation device, some substantial, further thermalcracking of the resid fractions occurs. To maximize conversion of residto lower boiling fractions, it is desirable to begin cracking the residfractions as early in the process as possible. According to the presentinvention, incipient thermal cracking is initiated in thehydroprocessing unit, then further thermal cracking is supported in thevisbreaking/separating step, thus maximizing the portion of the feedthat is vaporized. It is theorized that the increased concentration oflower boiling fractions created earlier in the process help assist orpromote the further breaking, cracking, and/or conversion of the residto lower boiling fractions. This includes conversion and cracking ofresid fractions having boiling points of up to and in excess of 1100° F+(593° C.) fractions, and even a portion of the resid fractions up to1400° F. (760° C.).

When the effluent from the hydroprocessing unit is heated (includingreheated) to above to 780° F. (415° C.), such as from 780° F. (415° C.)up to about 900° F. (482° C.), and processed in a visbreaker or otherseparator, still more thermal cracking of the 650° F.+ (343° C.+) residfractions occurs, including those resid fractions having a boiling pointof up to and in excess of 1050° F.+ (565° C.). At the highertemperatures closer to 900° F., the residence time may be shortened to acontact time that is unconventionally short as compared to prior arthydroprocessing or residfining contact time.

Surprisingly, this occurs without the formation of substantialquantities of coke, fouling, or solids in the unconverted 1050° F.+(565° C.) resid. This type of thermal cracking and vapor liquidseparation process may be described as “visbreaking.” Preferably theseparation and heating are integrated processes. The term “integrated”as used herein means “heat integrated,” in that the vapor liquidseparation device or visbreaker is connected to the steam cracker bypiping and is located substantially adjacent or relatively close to thesteam cracker, such that the feed may be heated in the convectionsection of the cracker, fed to the visbreaker, and then the overheadsfrom the visbreaker are fed back to the cracker, with minimal heat lossand preferably without requiring separating heating associated with thevisbreaking process.

The vapor liquid separation device is otherwise known as a “visbreaker,”“knock-out drum,” “knock-out pot,” and “vapor liquid separator,” whichterms may be used interchangeably. Reference is also made herein to the“visbreaker,” which serves as a vapor liquid separation device, with thedistinguishing feature that it generally operates at a highertemperature than some of the other separators to also facilitate somefurther thermal breaking and cracking of the feed. The terms “flashdrum,” “flash pot,” “visbreaker,” “vapor liquid separator,” and “flashseparator” are also well known terms having generally like meaning andmay be used herein substantially interchangeably. e.g., a knock-out potmay also be referred to as a visbreaker, or as a vapor-liquid separator.The term “flash” means generally to precipitate a phase change for atleast a portion of the material in the vessel or stream from liquid tovapor, via a reduction in pressure and/or an increase in temperature.Thus, “flash separation” may occur in a “flash drum” due to a reductionin pressure at the inlet to or within the drum.

In a more preferred embodiment the material is treated by visbreaking ormild thermal cracking to increase the proportion of vapor phase at theexpense of bottoms product. In some of the separation processes, such asin the high pressure separators and/or the flash separators, the feedmaterial also may be separated into a bottom, substantially liquidfraction, and an overhead, substantially vapor phase fraction. Thebottoms or liquid phase may include a resid fraction therein. The vaporfraction may also contain components derived from the resid fraction.Preferably, both the bottoms fraction and the vapor fraction effluentseach contain components derived from the resid fraction, though thecomposition of the resid fraction of the bottoms effluent will bedifferent from the vapor effluent. Thereby, each of the vapor stream andbottoms stream may be steam cracked.

Visbreaking is a well-known, non-catalytic, mild thermal crackingprocess that uses heat to convert or crack heavy hydrocarbonaceous oilsand resids into lighter, sometimes more valuable products, such asnaphtha, distillates, and tar, but not so much heat as to causecarbonization. The hydrocarbon feed may be heated, such as in a furnaceor soaker vessel to a desired temperature, at a desired pressure. Theprocess used may be, for example, the coil type, which provides for hightemperature-short residence time, or the soaker process, which providesfor lower temperature—longer residence time processing, as appropriateto obtain the desired broken product mix. The hydrocarbon feed streammay be heat soaked to reduce the viscosity and chain length of thehydrocarbon molecules, by cracking the molecules in the liquid phase.See, for example, Hydrocarbon Processing, September 1978, page 106.Visbreaking occurs when a heavy hydrocarbon, or resid, is heat soaked athigh temperature, generally from about 700° F. (371° C.) to about 900°F. (371° C. to about 482° C.) for several minutes before being quenchedto stop the reaction. Some of the resid molecules crack or breakproducing components that can be removed by standard atmospheric andvacuum distillation. Resid conversion in a visbreaker increases withincreasing temperature and increasing residence time. High severityvisbreaking maximizes conversion of 1050° F.+resid and is accomplishedby soaking the visbreaker feedstock at greater than about 840° F. (450°C.) for the longest time reasonably possible, without formingsubstantial coke or carbonization.

It is a key aspect of the present invention that, surprisingly, higherthan previously known visbreaking conversions can be accomplished onresid-containing crude streams or fractions that have been firstseverely hydroprocessed, e.g., crudes that are highly hydrogen saturatedand a substantial portion of the resid is already cracked) as comparedto un-hydroprocessed heavy crudes. The inventive, improved visbreakingprocess and behavior is believed to be due to the high hydrogen contentof the resid portion of the hydroprocessor effluent and due to theincreased lighter ends produced by the initial cracking that isperformed in the hydrogenation process.

In one preferred embodiment of the present invention, particularlysevere visbreaking, e.g., visbreaking at temperatures in excess of 800°F. (427° C.), is caused to occur in the vapor liquid separation device(visbreaker), preferably with the device integrated (heat integrated)with the steam cracker as described herein. The integrated vapor liquidseparation device can be taken off stream as often as every two weeksfor coke removal. This enables the separation device to operate with asignificantly higher coke yield than typical visbreakers, which may berequired to run several months between shut downs for coke removal, dueat least in part to the complexity and time required for decoking ofsuch systems. The visbroken vapor overheads, which include fractionsfrom the cracked resids, may then be fed to the steam cracker forfurther cracking into other products, including light olefin streams.

While lighter visbroken resid molecules (particularly resid materialshaving boiling points of less than 750° F. (<400° C.)) vaporize withoutadditional processing, steam stripping may be necessary and helpfuil tovaporize heavier visbroken molecules e.g., boiling points in excess of750° F. (>400° C.). The visbreaking reactions are rapid enough thatpurge steam and/or light hydrocarbons may be added to the vapor liquidseparation device to strip the visbroken molecules. This increases thefraction of the hydrocarbon vaporizing in the vapor liquid separationdevice. Heating may also be used to increase resid conversion.

Visbreaking may be controlled by modifying the residence time of theliquid phase within the vapor liquid separation device. In one preferredembodiment, the liquid phase level may be raised to substantially fillthe head space of the vapor liquid separation device, thus increasingresidence time of the resid molecules to an extent sufficient to affectat least partial visbreaking. Preferably the visbreaker is at least half(50%) full of liquid, more preferably, at least 75% full of liquid, andin some embodiments most preferably at least about 90% full of liquid,based upon the total volume of the vessel. The addition of heat may alsoaccelerate visbreaking in the liquid phase, the liquid residue of whichcollects as bottoms in the lower portion of the vapor liquid separationdevice. In one embodiment of the present invention, a heater in thelower section of a vapor liquid separation device is used in conjunctionwith the convection section of a steam cracking furnace, to provideadditional heat, if needed. The added heat may help keep the resid hotenough to continue the reaction and effect significant visbreakingconversion of the 750° F. (399° C.) to 1050° F. (565° C.) resid.

Preferred vapor liquid separation devices or flash drums, and theirintegration with pyrolysis units have previously been described in U.S.patent application Publication Nos. 2004/0004022, 20040004027, and2004/0004028, and more recently in U.S. application Ser. Nos. 11/068,615filed Feb. 28, 2005, Ser. No. 10/851,486 filed May 21, 2004, Ser. No.10/851,546 filed on May 21, 2004, Ser. No. 10/851,878 filed May 21,2004, Ser. No. 10/851,494 filed on May 21, 2004, Ser. No. 10/851,487filed May 21, 2004, Ser. No. 10/851,434 filed May 21, 2004, Ser. No.10/851,495 filed May 21, 2004, Ser. No. 10/851,730 filed May 21, 2004,Ser. No. 10/851,500 filed May 21, 2004, Ser. No. 11/134,148 filed May20, 2005, Ser. No. 10/975,703 filed Oct. 28, 2004, Ser. No. 10/891,795filed Jul. 14, 2004, Ser. No. 10/891,981 filed Jul. 14, 2004, Ser. No.10/893,716 filed Jul. 16, 2004, Ser. No. 11/009,661 filed Dec. 10, 2004,Ser. No. 11/177,076 filed Jul. 8, 2005; and Ser. No. 11/231,490, filedSep. 20, 2005. Another preferred apparatus effective as a vapor liquidseparation device for purposes of the present invention is described inU.S. Pat. No. 6,632,351 as a “vapor/liquid separator,” e.g., avisbreaker. Visbreaking is discussed in the aforementioned U.S. patentSer. Nos. 10/851,486; 11/134,148; 11/009,661.

In the process of the present invention, the visbreaker or vapor liquidseparation device preferably operates at a temperature of between about700° F. (371° C.) and 900° F. (482° C.), more preferably from about 750°F. (399° C.) to about 900° F. (482° C.), still more preferably fromabout 780° F. (415° C.) to about 900° F. (482° C.), and most preferablyfrom about 800° F. (427° C.) to about 875° F. (468° C.). Passing thehydroprocessed and partially cracked resid-containing material throughthe vapor liquid separation drum, while experiencing some pressurereduction therewith, to obtain an overhead vapor and liquid bottoms mayalso be referred to herein as “flashing” (or “flashed” or other variantdepending on the context).

Another aspect of the invention relates to the API gravity and sulfurcontent of the steam cracker feedstock. It is known that steam crackerfeed quality improves with increasing API gravity and decreasing sulfurcontent of the feed. The present inventors have surprisingly discoveredthat feedstocks rich in sulfur and in high boiling, polynuclearnaphthenes, polynuclear aromatics, and partially saturated polynucleararomatics, which tend to have lower API gravity, can be preferredfeedstocks to a steam cracker when first hydroprocessed.

It is also well known in the art that the specific gravity and sulfurcontent of crude oils increase with increasing boiling point. For thisreason, feedstocks rich in the vacuum resid from a crude oil with 15 to40 API gravity and 1 to 4 wt % sulfur may be some preferred feedstocksfor the process of the invention. Resid hydrotreating removes the sulfurthroughout the entire boiling range of the feedstock. Large amounts ofhydrogen are consumed removing the heteroatoms from the vacuum resid andsaturating polynuclear aromatics contained in the vacuum resid. Residhydroprocessing can be accompanied by both catalytic and thermalcracking of resid molecules into components that can be separated bystandard fractionation. Originally the inventors searched for residhydroprocessing conditions that obtained greater than 50% 1050° F.+conversion and greater than 90% sulfuir removal. The inventorssurprisingly invented a process whereby the 1050° F.+ conversion in theresidfiner (resid hydroprocessor) was not necessary because thisfunction could be readily accomplished by visbreaking the residfinereffluent in a separate step.

Resid hydroprocessing is used commercially in other refining processesto pretreat atmospheric resids (containing 25 to 35 wt % vacuum resid)for use as feedstock to an FCC unit. In this process, the coke yield onthe hydroprocessed resid is typically 5 to 8 wt %. This means that 92 to95% of the resid feed to the integrated residfiner and FCC unit isconverted to liquid and gas hydrocarbon products and only 5 to 8 wt % islost as low value coke.

The inventors were surprised to discover that similar results could beachieved by integrating Resid hydroprocessing, visbreaking, and steamcracking for the production of olefins. In the process of the invention,hydroprocessed resid is visbroken and the vaporized overheads from thevisbreaker are steam cracked. The inventors have surprisingly discoveredthat such a process produces 6 to 9 wt % visbreaker bottoms (analogousbut higher value than the coke produced in the FCC case), and 91 to 94wt % steam cracker products.

To take full advantage of the visbreaking capability of the process ofthe invention, preferred feedstocks may contain, in embodiments, 20 to50 wt % vacuum resid, and some feeds may even be whole crudes. Residhydroprocessing consumes large amounts of hydrogen. The inventors wereconcerned that hydrogen would be incorporated into the vacuum resid feedand yield a hydroprocessing effluent material only useful as fuel oil,having a lower value than the value of desired chemicals products (e.g.,light olefins). As previously mentioned, an objective of the process ofthe invention is to increase the hydrogen content of the steam crackerfeed while minimizing the increase in hydrogen content of the remainingresid, which is typically sold as low-value fuel oil. The integration ofsevere hydroprocessing and visbreaking surprisingly accomplishes thisobjective. Visbreaking effectively removes high hydrogen contentside-chains from cores made from polynuclear naphthenes and aromatics.Fouling in a visbreaker is limited by limiting the temperature andcontrolling the residence time, thereby avoiding the excessive formationof coke or fouling the equipment.

Crude or a resid-containing fraction thereof, particularly atmosphericresid, vacuum resid, or any resid or asphaltene containing refinery orchemical intermediate stream may also be a preferred feed to thehydroprocessor for the inventive process. When the feed comprisesgreater than about 0.1 wt %, or preferably greater than about 5.0 wt %asphaltenes, a vapor liquid separation device is advantageously used toremove the asphaltenes prior to entering the radiant section of thepyrolysis unit. Preferably, the vapor liquid separation device(visbreaker) may advantageously be heat integrated with the pyrolysisunit, as discussed above, so that the feed is preheated in theconvection section of the pyrolysis unit prior to entering the vaporliquid separation device. Thus, the term “integrated vapor liquidseparation device” as the term is used herein. In the alternative, avapor-liquid separation device may be substantially non-heat-integratedwith the cracker, so that the visbreaker has its own separate or asupplemental heat source such that removal of asphaltene and anynon-saturated or non-cracked resid occurs prior to the feed entering theradiant section of the pyrolysis unit. Both integrated andnon-integrated configurations are within the scope of the presentinvention.

Preferred feeds may include a hydrocarbon feedstream having a highconcentration of tar, and crude fractions such as topped crude (“toppedcrude” being the cut roughly from about 500-600° F. (260-315° C.) andhigher cut). Often topped crude is used as a synonym for atmosphericresid. This preferred feed may or may not contain appreciable amounts ofresid. However, any crude or resid containing crude fraction may beadvantageously treated according to the process of the present inventionto obtain chemicals products (light olefins and/or single ringaromatics) regardless of the amount of resid contained therein.

The following examples are meant to illustrate and not limit the presentinvention. Numerous modifications and variations are possible and it isto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

In the figures that follow, “HDP” is a hydrotreating apparatus, “HPS” isa high pressure separation device (e.g.,: drum with liquid level controlthat separates gas and liquid under pressure), “Steam Cracker” is athermal pyrolysis apparatus, and “Steam Cracker Product Recovery” is asystem that comprises one or typically several separation steps, e.g.,distillation columns. All of these apparatus or systems taken separatelymay be substantially conventional apparatus and are, separately, knownin the art.

Referring to the exemplary Figures, FIG. 1 is a process flow diagramillustrating an embodiment of the invention where a resid-containingfeed 8 is hydroprocessed in a hydroprocessing unit 10 and then passed toa steam cracker 20 to obtain various products 41-44, including olefins42. The design details of the steam cracker 20 by itself are not thesubject of the present invention. Processing conditions typically may bereadily determined by one of ordinary skill in the art. Non-conventionalsteam cracking designs known in the art, such as furnaces that areheated by direct mixing of super-heated solids or gasses with the liquidfeedstock comprising resid, are also contemplated by the inventors asbeing useful in the invention set forth herein.

One embodiment of the inventive process of preparing a resid-containingfeed for steam cracking comprises severely hydroprocessing the feed byhydroprocessing the feed at a temperature in excess of 700° F. (371°C.), preferably greater than 750° F. (399° C.), and more preferably inexcess of 780° F. (415° C.). The process also comprises furtherimproving the hydroprocessor effluent by holding, heating, and furtherconverting the effluent in a visbreaker type vapor-liquid separator.Preferably the visbreaker is heat-integrated with the steam cracker. Inthe heat integrated process as illustrated by FIG. 1, atmospheric resid8 is passed to a conventional hydroprocessor (HDP) 10, such as a fixedbed hydroprocessor. Numerous HDP units are commercially available,varying by catalyst and configuration, among other variables, such asavailable from ExxonMobil. The design details of an HDP by itself arenot the subject of the present invention. Processing conditions for theHDP typically may be readily determined by one of ordinary skill in theart. Petrochemicals recovery (light olefins and aromatics) will belargely affected by processing conditions chosen in the HDP 10, thevisbreaker type vapor liquid separator 30, and also in the steam cracker20.

The hydrogenated feed 14 from the HDP unit is then passed to one or moreseparation devices (not shown) to recover hydrogen, let down thepressure and reduce the temperature. The stream comprising hydrogen andlight carbon products, e.g., C2 and lower, may be recycled 12, and ahydrogenated effluent stream 14 comprising products from C2 boilingrange (C2+) and higher (e.g., up to 1500° F.) is recovered for furtherprocessing. Note that in many cases the recycle stream 12 may containH₂S, which is preferably removed, such as by membrane(s), absorbent(s),and the like, prior to entering the HDP unit 10. A bottoms stream fromthe HPS (not shown), may be split into two or more streams. In additionto being used for the process of the invention, the bottoms stream (notshown) can be recycled to the resid hydroprocessor 10 or furtherprocessed by conventional distillation and refining.

In the case where the feed 14 still contains asphaltenes, these may beadvantageously removed prior to entering the radiant section 24 of thesteam cracker 20. Examples of removal of the asphaltenes are discussedmore filly above and also in examples below. Although not shown indetail in FIG. 1, the hydrogenated C2+ stream 14 may be preheated in theconvection section 22 of the steam cracker 20 prior to being passed to avapor liquid separation device 30, wherein (nominally) 1050° F.+ resid,comprising asphaltenes if not previously removed, may be removed asbottoms product 32 from the vapor liquid separation device 30. The vapor34 is passed back to the convection section 22, preferably withoutcooling or condensing. The apparatus schematic designated “S/C furnaces”20 in FIG. 1 is the conventional illustration of a steam crackerfurnace, the details of which, again, are not the subject of the presentinvention except for the integration of the vapor liquid separationdevice 30, which has been described in the references discussedelsewhere herein. The separation device 30 is preferably functions as avisbreaker, in that the device 30 separates, temporarily holds, andfurther heats a stream that has been previously heated in thehydroprocessor. Thereby, initial cracking is caused in thehydroprocessor, creating some lighter fractions, and then subsequentcracking is caused in the visbreaker. Substantially completevaporization can be achieved by the light ends created in thehydroprocessor, supplemented by the lighter molecules produced byvisbreaking, and further supplemented by the steam injected into and/orahead of the visbreaker, and optionally by the flashing pressure drops.The separator 30 is also preferably heat integrated with the cracker 20,in that the separator is located close enough to the steam cracker 20that preferably no additional or separate heat is needed for theseparator to facilitate the visbreaking type separation in the separator30. Thereby, the separator 30 may be “integrated” with the steam cracker20. The pressure is preferably reduced to between about 50 and 100 psigbefore the separated streams are sent to the steam cracker.

Although not shown in detail in FIG. 1, in a preferred embodiment, thehydrogenated C2+ stream 14 is heated in the convection section 22 of thesteam cracker 20 at a sufficient temperature to initiate thermalcracking of the hydrogenated resid prior to being passed by line 33 to avapor liquid separation device, wherein (nominally) 1050° F.+ resid,comprising asphaltenes, is removed as bottoms product 32 from the vaporliquid separation device 30. Steam (not shown) can be added to the vaporliquid separation device to increase the fraction of the feedstockremoved as vapor 34. The residence time of the liquid in the vaporliquid separation device 30 can be increased to increase the fraction ofthe feedstock removed as vapor 34. It is a further inventive aspect ofthis invention that raising the liquid level in the visbreaker separatormay increase liquid residence time to further increase conversion of theresid fractions, for a given treating temperature (particularly thehigher boiling resid). The visbreaker comprises a vapor liquidseparation vessel or device that separates the vapor fraction from theliquid fraction, and wherein the separation vessel includes a liquidvolume that preferably occupies at least 50% of the volume of thevessel. Preferably, the liquid level of the separation vessel will be atleast about equal to or greater than 75% by volume of the vessel, stillmore preferably greater than about 80%, and most preferably greater thanabout 90% of the vessel volume.

The vapor 34, including resid molecules that have been thermally cracked(also known as destructive distillation), may be passed back to theconvection section 22. In this way the convection section 22 of thesteam cracker 20 may convert 1050° F.+ vacuum resid to lightermolecules. Ultimately, fuel oil yield is reduced and petrochemicalsyields (e.g., the desired light olefins and single ring aromatics) areincreased. If the temperature is too high or the residence time of thefeedstock is too long, in the hot visbreaker vapor liquid separationdevice 30, coke formation may initiate. If this happens, the process mayundesirably fill the vapor liquid separation device 30 with coke, whichnecessitates shutting down the process. In a preferred embodiment, thetemperature and residence time in the vapor liquid separation device 30are controlled to allow only a small amount of coking. For ex ample,every 15 to 40 days the steam cracker may be shut down to readily removean acceptable amount of coke from the radiant section 24 of the furnace20, the lines, and/or from the separator 30, if necessary. The processof the invention may use known methods and facilities to remove cokefrom the vapor liquid separation device 30 and the piping in theconvection 22 and radiant 24 sections of the steam cracker furnace 20.Because of this synergy between visbreaking and steam cracking, theprocess of the invention can visbreak the resid in the feedstock at ahigher severity than conventional visbreakers, which are designed to runfor several months before decoking is required.

The apparatus schematic designated “S/C furnaces” 20 in FIG. 1 is theconventional illustration of a steam cracker furnace, the details ofwhich, again, are not the subject of the present invention except forthe integration (not shown in FIG. 1) of the vapor liquid separationdevice, which has been described in the references discussed elsewhereherein.

In another embodiment, all or any fraction of the hydroprocessoreffluent 14 comprising 1050° F.+ (565° C.+) resid may be heated in asteam cracker 20 or by separate heat source, to a temperature highenough to initiate thermal cracking but low enough to avoid significantcoking. The cracked stream may be held at this temperature for a longenough time to achieve from about 5 wt % (low severity) to about 60 wt %(high severity) conversion of the 1050° F.+ resid (i.e., conversion ofmaterial from higher boiling resids, including the 1050° F. (565° C.)resids to lower boiling point material), but short enough to avoidsignificant coking. The optimal temperature and time (“time attemperature”) is different for each specific feedstock and can bedetermined by one skilled in the art without more than routineexperimentation. The time at temperature is selectively ended byquenching the hot bottoms material to prevent fouling or coking. Thoseskilled in the art in possession of the present disclosure wouldrecognize this generally as visbreaking. In the visbreaking vapor liquidseparation step, wherein (nominally) the unbroken 1050° F.+ resid and/orasphaltenes are removed as bottoms product from the vapor liquidseparation device, and all or a fraction of the visbreaker vaporeffluent 34, is passed to the steam cracker 20, and preferably to theconvection section 22 prior to entering the radiant section 24. Theseparated vapor is further processed and cracked in the radiant section24 to yield steam cracker effluent 26 comprising the desired lightolefins 42.

It is one of the important advantages provided by the present inventionthat by means of the high severity hydroprocessing and visbreaking ofthe hydroprocessor effluent 14, whether in a visbreaker configured priorto the steam cracker and having supplemental or separate heat source, orintegrated with the steam cracker, that high conversion, such as atleast 50 wt % or even greater than 50 wt %, such as up to 55 wt % andeven up to about 60 wt % of the hydrogen-rich 750° F.+ (399° C.+) residand even a significant portion of the 1050° F.+ (565° C.+) material, canbe achieved. This provides a steam cracker feedstock 34 (or feedstock tothe radiant section 24, in the case of the visbreaker integrated withthe convection section 22 of the steam cracker) having greater than 13wt % hydrogen. The bottoms product 32 of the visbreaker device 30, whichin some embodiments may comprise less than 11.5 wt % hydrogen, may beused as. fuiel oil and/or recirculated to the hydroprocessor, or fed toanother processing unit, such as a catalytic conversion system.

In an embodiment, illustrated by the schematic shown in FIG. 6, theprocess of the invention integrates the steps of resid hydroprocessing10, hydroprocessed resid visbreaking 30, and steam cracking 20.Conventional visbreakers can be operated to perform the operationalparameters of the present invention, to separate a distilled vaporand/or liquid from unconverted resid feedstock. The distilled liquidand/or vapor from the resid hydroprocessor 10 and/or the visbreaker 30are processed in a steam cracker 20 to produce petrochemicals. At leastone significant advantage of this embodiment is that there is no need todirectly integrate a vapor liquid separation device with the convectionsection of the steam cracker 20.

The product of the steam cracker 20 is sent to the steam cracker productrecovery section (not shown in FIG. 6) where various products may berecovered by separation, typically by distillation. The “chemicals”stream comprises ethylene, propylene, and butenes. The separations areper se conventional and not the subject of the present invention.

Certain variations will immediately become apparent to one of ordinaryskill in the art. As an example, one or more of the vapor liquidseparation device may be exchanged with other separation devices, suchas membranes and integration with the steam cracker, while a preferredembodiment, is optional. Removal of the asphaltenes, however, is highlypreferred prior to the radiant section of the thermal pyrolysis unit(steam cracker). Membranes are particularly useful to separate, forinstance, polar from non-polar species (for instance, prior to the HDPunit).

In the embodiment shown in FIG. 6, where the process of the inventionintegrates the steps of resid hydroprocessing 10, hydroprocessed residvisbreaking 30, and steam cracking 20, conventional visbreakers can beoperated to separate a distilled vapor and/or liquid from unconvertedresid feedstock. The distilled liquid and/or vapor from the residhydroprocessor and/or the visbreaker are processed in a conventionalsteam cracker to produce petrochemicals. At least one significantadvantage of this embodiment is that there is no need to directlyintegrate a vapor liquid separation device with the convection sectionof the steam cracker.

FIG. 2 is a process flow diagram illustrating an embodiment of theinvention where a resid-containing feed 8 is hydrotreated 10 and thenpassed 14 to a steam cracker 20 to obtain various products includingolefins.

In an embodiment of the process illustrated by FIG. 2, a feed 8, whichin a preferred embodiment is atmospheric resid, is passed to aconventional hydroprocessor (HDP) 10, such as a fixed bedhydroprocessor. Again, the design details of the HDP are not per se thesubject of the present invention. Illustrative processing conditions areprovided in FIG. 2 for the HDP step 10, however as would be recognizedby one of ordinary skill in the art, these may vary and may bedetermined by routine experimentation. Actual conditions for the one ormore HDP apparatus will vary in accordance with the specific feed and/ordesired products in integration with the steam cracker conditions andvisbreaker conditions, but good starting point would be 2200±500 psig(total pressure), 725±100° F. (measured at reactor outlet), 3000±200SCFB hydrogen processed at 0.1 to 0.3 WHSV.

The hydrogenated feed 14 is passed to a high pressure separator 15operating at the conditions such as specified in FIG. 2, which may,again, vary and be determined by one of ordinary skill in the art byroutine experimentation, depending on the feed and the operatingconditions of the other apparatus in the system shown. The overheads 16,passing through a-heat exchanger 17 illustrated in the conventionalmanner of a circle with arrow passing through, may consist of distillateboiling at, for example, 650° F. and below. The cooled overhead 18 maybe sent to a second HPS 19, as illustrated in FIG. 2, separating thestream at the 90° F. point, as shown, to yield a bottoms 21 comprisingC3 material and higher carbon numbers (including naphtha and heavydistillate), which may be passed to the steam cracker 20, and anoverheads 23 comprising hydrogen, methane, ethane, and H₂S, theoverheads being recycled, preferably after removal of H₂S by, forinstance, membrane, absorbent, and the like.

In the exemplary embodiment described and illustrated in FIG. 2, thebottoms 35 from the first HPS 15 may comprise the material boiling above650° F. In some embodiments, the bottoms 35 may be recycled or mixedwith the bottoms 21 of the 2^(nd) HPS 19 and then depressured 55. Inpractice, typically a portion (such as 0 to 90 wt % or 40 to 60 wt %)will be recycled (not shown) and a portion 35 (such as 10 to 100 wt % or40 to 60 wt %) will be mixed and depressured. Mixing with the 90° F.liquid cools the liquid 35 from the first HPS 15 reducing the amount offlashing that occurs upon depressuring.

In another embodiment, the combined liquid effluents 14 from the residhydroprocessor 10, comprising resid and for example, Vacuum Gas Oil(VGO), may be preheated in the convection section of the steam cracker20 and then the vapor from the integrated vapor liquid separation deviceis passed back into the convection section and then introduced or passedinto the radiant section of the steam cracker, where it is cracked. Thebottoms from the integrated vapor liquid separation device, consistingof (in the present preferred embodiment) 1050° F.+ cut, comprisesasphaltenes.

The product 26 of the steam cracker 20 may be sent to the steam crackerproduct recovery section 40, where various products 41-44 may berecovered by separation, typically by distillation, as shown in FIG. 2.The “chemicals” stream 42 comprises, for example, ethylene, propylene,and butenes. Each steam cracker 20 may be integrated with its ownproduct recovery apparatus 40 or a single product recovery unit 40 mayhandle both steam cracker effluents 26, 38.

Certain variations will immediately become apparent to one of ordinaryskill in the art. As an example, other separation devices, such asmembranes or vacuum towers, can be added. Membranes are particularlyuseful to separate, for instance, polar from non-polar species (forinstance, prior to the HDP unit) or aromatic from non-aromatic species(for instance, after the second HPS unit in FIG. 2 and prior to thesteam cracker, passing non-aromatics to the steam cracker and recyclingaromatics to the hydroprocessing unit).

FIG. 3 illustrates another preferred embodiment of the invention. FIG. 3is similar to FIG. 2 except in FIG. 3, tar 44 from the product recoveryunit 40, heated to about 100° C. to about 200° C. to maintain fluidity,and now containing substantially no metals and comprising very littlesulfur, may be passed to the HDP 10, preferably being diluted with oneor more of the 650° F.+ recycle 23 and/or feed 8, or portion of one orboth of these materials.

FIG. 4 illustrates still another embodiment of the invention. FIG. 4 issimilar to FIG. 3, except a second HDP unit 70, a second heat exchanger72, and a third HPS unit 74 is provided. As shown in FIG. 4, material 76from the third HPS unit 74 (e.g. 400-650° F. (204-343° C.) liquid) issent as feed to the second HDP unit 70. Tar 44 is optionally recycled tothe second HDP unit 70. FIG. 4 further employs a vapor liquid separationdevice 25 (Flash in FIG. 4) to separate the about 900-36 from the about900° F.+ 37 resid. The 900° F.− vapor 36 (mixed with steam 31) may bepassed directly to conventional steam crackers 20 without an integratedvapor liquid separation device. The about 900+ resid 37 may be passed tosteam crackers 50 that comprise an integrated vapor liquid separationdevice 30 to be subjected to visbreaking. The vapor liquid separationdevice 30 can be operated at a variety of conditions as is readilyunderstood by those skilled in the art. In another variation (not shown)a portion of the tar 44 can be mixed with the atmospheric resid 8 and aportion mixed with the bottoms product 76 of the third HPS unit.

It will be recognized by one of ordinary skill in the art in possessionof the present disclosure that a visbreaker may be arranged prior to oneor more of the steam crackers in any one of FIGS. 1-4 discussed above.With the visbreaker step before the thermal pyrolysis step, inaccordance with the present invention, the vapor liquid separationdevice, integrated with the thermal pyrolysis furnace, becomes optional.This can be illustrated by reference to the following example as well asadditional figures described below.

Referring to FIG. 5, visbreaking is accomplished in a vapor liquidseparation device 30 integrated with the steam cracker 20. In an exampleillustrated in FIG. 5, crude oil was distilled at about 1 atmospherepressure until the remaining oil reached 600° F. (about 315° C.). Theheavy oil (resid) is analyzed (see Table 1). The heavy oil (resid) wasmixed with hydrogen and passed through a hydroprocessor 10, processed at0.2 WHSV, 695° F., and 2000 psig total pressure. The hydroprocessoreffluent 14 is analyzed (see Table 1). The liquid product 14 from thehydroprocessor is then subjected to vacuum distillation (not shown inFIG. 5) to separate the vacuum resid. The distillation yields 82 wt %distillate (1050−) and 18 wt % vacuum resid (1050+). The analysis isprovided in Table 1.

The results of visbreaking 30 the 18 wt % vacuum resid can be estimated.Due to the high hydrogen content (12.5 wt %) of the feedstock 14, highconversions in the visbreaker 30 are possible before the onset ofsubstantial coke formation. Severe visbreaking will produce 40% yield ofvacuum resid containing up to 10.8 wt % hydrogen and a 60 wt % yield ofoverheads with a hydrogen content of 13.5 wt % H. The calculatedhydrogen (H) content of the visbreaker overheads is close to the Hcontent of the distilled residfiner liquids. Thus, it can be assumedthat addition of the visbreaker overheads to the distilledhydroprocessed liquids will not significantly change steam crackingyields. The 93 wt % distillate material stream 34 from the residhydroprocessing step may then be used as steam cracker feedstock. Theyields from steam cracking are provided in Table 2 and are substantiallythe same as the yields shown in FIG. 5. The experiments reported inthese examples were carried out to simulate operations at a commercialscale, as illustrated by FIG. 5 and as described throughout the spec.TABLE 1 Hydroprocessor Crude Atm Resid Effluent 1050− 1050+ API Gravity17.8 27.0 30.0 17.5 wt % H 11.3 12.9 13.1 12.5 wt % S 4.2 0.15 0.01 0.3wt % C5- 0.0 3.0 5.0 0.0 wt % C5-1050 F 64.0 80.0 95.0 0.0 wt % 1050+36.0 18.0 0.0 100.0 Paraffins 16.0 27.0 naphthenes 19.0 39.0 1 ringaromatics 8.0 26.0 2 ring aromatics 15.0 7.0 3 ring aromatics 17.0 2.0 4ring aromatics 13.0 0.0

TABLE 2 Steam Cracking Yields: Hydroprocessor 1050− Liquids Steamcracker Yields, wt % fuel gas 10 ethane/propane 5 ethylene 21 propylene13 C4's 10 BTX 9 Other SCN 11 tar and gas oil 21

The results in Table 1 suggest that the feed to the residhydroprocessing step contained 36 wt % of material boiling above 1050°F. The product from the hydroprocessing step contained 18 wt % ofmaterial boiling above 1050° F. Conventional hydroprocessing resulted inabout 50% conversion of the vacuum resid fraction of the feedstock. Thismeans that hydroprocessing followed by vacuum distillation results in aproduct with 18 wt % vacuum resid, and close to 80 wt % liquids suitablefor steam cracker feedstock. The 18 wt % vacuum resid is substantiallyenriched in hydrogen but can only be sold as low sulfur fuel oil unlessfurther processed. It is desirable to decrease the yield of low sulfurfuel oil and increase the yield of steam cracker feedstock. Thevisbreaking step converts roughly 60 wt % of 12.5 wt % H, 1050° F.+hydroprocessor effluent into steam cracker feedstock. The unconverted1050° F.+ residfiner effluent is 10.8 wt % H which is similar to the Hcontent of the feedstock to the resid hydroprocessor (11.3 wt %). Thecombination of resid hydroprocessing and visbreaking results in anoverall 80% conversion of the vacuum resid portion of the feedstock tothe hydroprocessor. The 7 wt % low sulfur fuel oil (“resid” in FIG. 5)has similar hydrogen content to the resid hydroprocessor feedstock soalmost none of the hydrogen consumed in the resid hydroprocessor is soldto customers as fuel oil. Instead, resid hydroprocessing the feedstockenables visbreaking to be carried out at unusually high conversion.Feeding severely hydroprocessed resid to a visbreaker is also believedto be a significant advantage of embodiments of the present inventionheretofore unrealized in the art, since it is not at all obvious why itwould be useful to visbreak a feedstock according to the presentinvention, as opposed to sending the feedstock to a coker or to an FCCunit as in the prior art.

Resid hydroprocessing using feedstocks and conditions similar to thosecited in the tables above is practiced to pre-treat resid for use asfeedstock to an FCC unit. In an FCC unit, the hydroprocessed resid maybe converted into liquid and gas products with a coke yield of about 5to 6 wt %. It is highly surprising that resid hydroprocessing followedby visbreaking and steam cracking results in similar overall residconversion to liquid and gas products. The byproduct from residhydroprocessing, visbreaking, and steam cracking is low sulfur fuel oil(“resid” in FIG. 5) which has significantly higher value than coke onFCC catalyst.

Two key parameters for steam cracker feedstock are wt % hydrogen and wt% polynuclear aromatics. Ethylene yield may closely correlate with wt %hydrogen and tar yield may closely correlate with wt % polynucleararomatics. The resid hydroprocessing of FIG. 6 results in a product withhydrogen content typical of ordinary VGO's used in the steam crackingart, but with significantly lower concentrations of polynucleararomatics.

A consequence of steam cracking feedstocks with >20 wt % aromatics istar yields between 10 and 20 wt %. The process of the invention providesan opportunity to eliminate or greatly reduce tar as a product byrecycling the tar to the hydroprocessor. Tar hydrogenation followed bysteam cracking enables substantially complete conversion of tar tolighter products. This is a desirable but not solely necessary aspect ofthe process of the invention. Steam cracker tar was previously notnormally hydroprocessed. Problems with fouling, incompatibility, and lowreactivity were anticipated.

While the above embodiment has been illustrated using, as feed,atmospheric resid, any crude or fraction thereof may benefit from thepresent invention. In preferred embodiments, the feed is selected fromat least one of heavy crude oil, vacuum resids, fuel oil, FCC cycleoils, coker gas oils, cracker tar, topped crude, and any other feedcontaining resid and/or a high concentration of multicyclic aromaticspecies. Mixtures of such feeds, such as provided by crude, are alsopreferred. FIGS. 1-6 represent only a small number of the countlessnumber of possible optimizations directed to minimize refinery energyusage and maximize efficient use of hydrogen and hydrocarbon feedsources.

By way of further non-limiting example, illustrating yet still anotherembodiment, which may be a more preferred embodiment, the source ofhydrogen used in the system (e.g., in the HDP units) may be from amethane source, particularly a remote methane. Use of remote methane asa source for hydrogen is described in U.S. Pat. No. 6,784,329.

Maximizing the value of remote methane resources is an old problem inthe industry. While methane commands a premium value for the productionof hydrogen, frequently, neither chemical can be shipped long distanceseconomically. Use of methane from remote areas or other sources of highand/or underutilized methane volumes for hydrogenation of the feedstocksto the hydroprocessing unit may facilitate improved economic generationof valuable products from steam cracking. The term “remote” is notlimited to distant but rather is defined more broadly to includesubstantially any suitable source of methane and/or hydrogen that mightotherwise only have less valuable options or opportunities than for usein the described processes. This includes methane produced in variousparts of the world in substantial volumes, that may have limited,costly, or otherwise unfavorable access to markets or limited use. Suchmethane may be converted to hydrogen for use in the inventive processes.

Crude oil typically contains a minimum of about 10 wt % hydrogen. Fullyhydrogenated crude (where the crude contains substantially onlyparaffins and cycloparaffins, having >95 wt % conversion of sulfur,nitrogen, and oxygen-containing impurities), may contain as much asabout 14-15 wt % hydrogen. This saturated cracker feed is a highlypreferred feed in the present invention. Petrochemical yields of crudehaving 14.5 wt % hydrogen may be increased substantially over crudehaving 10-11 wt % hydrogen.

A convenient method of converting methane to hydrogen remotely is byexploitation of a steam reforming unit, which are available fromnumerous commercial sources. In steam reforming, light hydrocarbons suchas methane are reacted with steam to form hydrogen and carbon monoxide.The reaction may be illustrated by the well-known Syngas equilibriumequation:CH₄+H₂O←→3H₂+CO

Typically Syngas is exploited by, for instance conversion into loweralkanes by, for instance Fischer-Tropsch catalysts, which may be fedinto a naphtha cracker to generate ethylene. However, according to thepresent invention, hydrogen may be extracted from the product side ofthe equation and used to hydrogenate crude or resid-containing fractionthereof. The carbon monoxide may be further reacted with steam to formadditional hydrogen (and carbon dioxide) in the water gas shiftreaction. Other reactions may generate hydrogen from methane, forinstance, reaction of methane with oxygen to produce hydrogen and carbonmonoxide (partial oxidation).

The present invention thus allows the producer to locate thehydroprocessing HDP unit close to the methane source (e.g., remotemethane), hydrogenate feed comprising resid (either from well-headslocated near the remote methane or by shipping the resid-containingmaterial to the remote methane), and then ship the product of the HDPunit to the steam cracker (or locate the steam cracker at the remotesource).

The present invention provides numerous advantages besides those pointedout above. In preferred embodiments, the invention provides for one ormore of the following advantages: (a) use of lowest cost feedstock(feeds high in 1050+ resid and/or polynuclear aromatics, and/orheteroatoms; use of remote methane); (b) high combined 1050° F.+conversion when the conversion in the residfiner and the visbreaker arecombined, (c) low cost integration of feed, including hydrogen, withsteam cracker facility, substantially eliminating transportation costs;(d) single feed simplifies pyrolysis unit design and/or maintenance; (e)reduces problem of treatment/disposal of resid/asphaltene/tar/sulfur andnitrogen polynuclear molecules (“bottom of barrel”); (f) providesalternative to naphtha reforming for the production of aromaticsproduct.

Having thus described the invention generally and with reference tospecific embodiments, in preferred, exemplary embodiments, the inventionrelates to processes comprising: (i) obtaining a feedstock comprising aneffluent from a resid hydroprocessing unit that was processed atrelatively severe conditions, such as preferably in excess of 700° F.(371° C.), and more preferably in excess of 750° F. (399° C.); (ii)separating (e.g., visbreaking) the effluent in a separator, into anoverhead stream and a bottoms stream, wherein the overhead streamincludes a vapor; then (iii) the overhead from the visbreaker is passedto the radiant section of steam cracker; (iv) obtaining an effluent fromthe steam cracker comprising olefins.

This may be modified or enhanced by one or more of the following evenmore preferred embodiments: wherein step (iii) is characterized bypassing the overhead from the visbreaker to a steam cracker as vaporwithout cooling or condensing; wherein step (iii) comprises passing theoverhead from the visbreaker to the convection section of the steamcracker and then to the radiant section of the steam cracker; wherein(ii) comprises passing the effluent to the convection section of a steamcracker and then visbreaking the effluent in a vapor liquid separationdevice; wherein (ii) the visbreaker/vapor liquid separation device isheat integrated with the steam cracker; wherein step (i) is furthercharacterized by hydroprocessing a feed comprising crude or crudefraction to obtain a hydroprocessed crude or hydroprocessed crudefraction, wherein the hydroprocessed crude fraction comprises resid;wherein step (i) is further characterized by hydroprocessing a feedcomprising crude or crude fraction containing >20 wt % or >25 wt %,or >30 wt % 1050° F.+ resid, and >20 wt % or >25 wt %, or >30 wt %aromatics, and <25 wt %, or <20 wt %, or <15% paraffins to obtain ahydroprocessed crude or hydroprocessed crude fraction, wherein thehydroprocessed crude fraction comprises resid; wherein visbreakingoccurs under suitable conditions (generally from about 700° F. (371° C.)to about 900° F. (482° C.), or in other embodiments greater than about850° F. (>450° C.) to about 900° F. (482° C.), or within the preferredrange of operation of the vapor liquid separation device of about 425°C. to about 467° C., or within ranges from any of the lower limits toany of the upper limits set forth in this parenthetical expression, suchas 425° C. to 482° C. and 450° C. to 467° C.) to provide from greaterthan about 5 wt %, preferably about 5 wt % to about 60 wt %, morepreferably 50 wt % to about 60 wt %, still more preferably >50 wt % toabout 60 wt %, yet still more preferably >55 wt % to about 60 wt %conversion of >1050° F.+ resid to <1050° F.+ material (in other wordsfor a sufficient “time at temperature” to provide for the aforementionedconversions); including a step of visbreaking the hydroprocessed crudeor hydroprocessed crude fraction followed by a step of separating toobtain a resid containing fraction and a non-resid containing fraction,then steam cracking the non-resid containing fraction to obtain aproduct comprising olefins; wherein the feed comprises crude or crudefraction containing at least one impurity selected from: (a) sulfur inthe amount of greater than 1 wt %, more preferably greater than 3 wt %,based on the weight of the feed; (b) resid in the amount of greater than10 wt %, preferably greater than 20 wt %, more preferably greater than30 wt %, based on the weight of the feed; (c) naphthenic acids asmeasured by a TAN of ≧1.0, preferably ≧1.5, more preferably ≧2.0, stillmore preferably ≧2.5 mg KOH/g oil, yet still more preferably ≧3.0 mgKOH/g oil (ASTM D-664); wherein step (i) saturates at least 20 wt %,preferably at least 40 wt % of the aromatic species in the feed; whereinthe product of step (ii) further comprises tar and wherein the tar isrecycled to the feed in step (i); wherein the feed comprises steamcracker tar.

Another preferred embodiment of the invention relates to an integratedhydroprocessing and steam cracker system for making olefins from crudeand crude fractions comprising resid, the system comprising at least onehydroprocessing apparatus, at least one high pressure separator, atleast one visbreaker, at least one steam cracker optionally having avapor liquid separation device integrated therewith, and at least onesteam cracker product recovery apparatus. This may be modified orenhanced by one or more of the following: the system further comprises asteam reformer co-located with the hydroprocessing apparatus configuredso as to provide hydrogen to the hydroprocessing apparatus; the systemfurther characterized as comprising in series and in the following ordera visbreaker and at least one steam cracker optionally having a vaporliquid separation device integrated therewith; wherein the system doesnot comprise the integrated vapor liquid separation device; wherein thesystem comprises the integrated vapor liquid separation device; whereinthe visbreaker is integrated with the steam cracker between theconvection section and radiant sections. Yet another preferredembodiment includes a process for making olefins from a hydrocarbon feedcomprising feeding -the feed through a system comprising ahydroprocessing apparatus and a steam cracker, the improvementcomprising feeding a resid-containing material directly into ahydroprocessing apparatus and hydroprocessing the resid-containingmaterial, visbreaking the effluent of the hydroprocessing apparatus in avisbreaker, and then obtaining at least one of a C2-C6 olefin and singlering aromatic species as an effluent of a steam cracker, which may bemodified or enhanced by an embodiment wherein substantially all of theeffluent of the visbreaker is provided to the convection section of asteam cracker where it is mixed with steam and then sent to a vaporliquid separation device integrated with the steam cracker to provide afirst stream consisting essentially of vapor material and a secondstream consisting essentially of non-vapor material, and then crackingthe vapor material in the radiant section of the steam cracker andrecovering an effluent of the steam cracker comprising at least one of aC2 to C6 olefin and single ring aromatic species. Yet still anotherembodiment of the invention is a process comprising providing afeedstream comprising resid to a system according to any one of thesystem embodiments set forth in the present disclosure, particularly thepreferred embodiments set forth in this paragraph, and obtaining fromthe steam cracker product recovery apparatus at least one productselected from C2-C6 olefins and single ring aromatics.

Still other preferred embodiments of the inventive processes may bedescribed as follows: (i) Obtaining an effluent from a residhydroprocessing unit, wherein the effluent comprises 650° F.+ (343° C.+)resid; (ii) separating the effluent in a separator, into an overheadstream and a bottoms stream; then (iii) passing the overhead stream fromthe separator to a steam cracker; (iv) steam cracking the overhead inthe steam cracker and obtaining a steam cracker product from the steamcracker, the product comprising olefins. Preferably, step (iii) ischaracterized by passing the overhead from the separator to the steamcracker as vapor. The separator may comprise at least one of avisbreaker, a flash drum, a high pressure separator, and a vapor liquidseparator. It is understood that arguably, there may be very littledifference in these items and the terms are commonly usedinterchangeably. The step of separating may comprise visbreaking theeffluent and separating a vapor fraction from a liquid fraction.

Preferably, the process also comprises the step of flashing the effluentthrough at least one pressure drop to reduce the pressure of theeffluent by at least one-half of the pressure of the effluent in thehydroprocessing unit, prior to steam cracking the effluent in the steamcracker. In practice, the pressure drop may occur substantially inconjunction with the visbreaking operation to cause the flashing of aportion of the liquid fractions to vapor fractions within thevisbreaker/separator. At least one of the pressure drops occurssubstantially immediately prior to the separator or within theseparator. It is preferred that thermal cracking of the feedstock beginin the hydroprocessing unit and that the cracking continue in thevisbreaker/separator. Surprisingly, the severe hydroprocessing plus thesevere visbreaking serves to break down a substantial portion of the650° F.+ (343° C.+) resid and even a substantial portion of the 1050°F.+ (565° C.+) resid. Thereby, a majority by weight of the bottomsfraction from the separation step comprises resid having a boiling pointof at least 900° F. (482° C.), and preferably of at least 1050° F.+(565° C.+). In preferred processes, the step of separating includesseparating the effluent in a vapor liquid separation vessel, such as aflash drum or visbreaker, wherein the vessel is at least one of (i) heatintegrated with the steam cracker, such as by location and/or connectivepiping so as not to require a separate heat source, and/or (ii) heatedwith a heat source other than the steam cracker.

In preferred embodiments, the effluent in the separator/visbreaker isheated to a temperature of at least 750° F. (399° C.), more preferablyto a temperature of at least 800° F., still more preferably to atemperature of at least 850° F. (454° C.), yet still most preferably toa temperature of from about 750° F. (399° C.) to about 900° F. (482°C.). Also preferably, the effluent in the separator/visbreaker isretained in the separator for at least a determined minimum amount oftime and not longer than a determined maximum amount of time. This iscommonly the practice with visbreaking and flash drum type operationsand is necessary to quench the bottoms liquid stream to stop thereaction from proceeding to fouling or coking, while still permittingadequate time for the reaction to sufficiently crack a substantialportion of the resid, including the 1050° F.+ (565° C.+) resid intolighter components. The exact timing will depend upon the crudefeedstock properties and the properties of the effluent in theseparator.

Preferably, the inventive processes comprise the step of processing theresid-containing hydrocarbon feed in the hydroprocessing unit, whereinthe processing comprises combining the feed with hydrogen at atemperature of from about 750° F. (399° C.) to about 900° F. (482° C.).Preferably the hydrogen is from a remote source. The hydrogenationprocess may be performed at a pressure of from about 1000 psig to about4000 psig, and the hydroprocessing saturates at least 20 wt %,preferably at least 40 wt % of the aromatic species in the feed.Preferred processes also include adding steam to at least one of theeffluent from the hydroprocessing unit and the separator. After crackingthe vapor fraction in the steam cracker, the desired olefins and otherproducts may be recovered by other known processes.

The meanings of terms used herein shall take their ordinary meaning inthe art; reference shall be taken, in particular, to Handbook ofPetroleum Refining Processes, Third Edition, Robert A. Meyers, Editor,McGraw-Hill (2004). In addition, all patents and patent applications,test procedures (such as ASTM methods), and other documents cited hereinare filly incorporated by reference to the extent such disclosure is notinconsistent with this invention and for all jurisdictions in which suchincorporation is permitted. Also, when numerical lower limits andnumerical upper limits are listed herein, ranges from any lower limit toany upper limit are contemplated. Note further that Trade Names usedherein are indicated by a ™ symbol or ® symbol, indicating that thenames may be protected by certain trademark rights, e.g., they may beregistered trademarks in various jurisdictions.

The invention has been described above with reference to numerousembodiments and specific examples. Many variations will suggestthemselves to those skilled in this art in light of the above detaileddescription. All such obvious variations are within the full intendedscope of the appended claims.

1. A process comprising: (i) hydroprocessing a feed comprising crude ora crude fraction comprising resid in a hydroprocessing unit at atemperature sufficient to promote incipient thermal cracking of theresid; (ii) obtaining an effluent from the hydroprocessing unit; (iii)separating the effluent in a separator, into an overhead stream and abottoms stream; then (iv) passing the overhead stream from the separatorto a steam cracker; (v) steam cracking the overhead in the steam crackerand obtaining a steam cracker product from the steam cracker, theproduct comprising olefins.
 2. The process of claim 1, wherein thetemperature sufficient to promote incipient thermal cracking is fromabout 750° F. (399° C.) to about 900° F. (482° C.).
 3. The process ofclaim 1, wherein the temperature sufficient to promote incipient thermalcracking is at least about 780° F. (415° C.).
 4. The process of claim 1,wherein the temperature sufficient to promote incipient thermal crackingis at least about 800° F. (427° C.).
 5. The process of claim 1, whereinstep (iv) is characterized by passing the overhead from the separator tothe steam cracker as vapor.
 6. The process of claim 1, wherein theseparator comprises at least one of a visbreaker, a flash drum, a highpressure separator, and a vapor liquid separator.
 7. The process ofclaim 1, wherein the step of separating comprises visbreaking theeffluent and separating a vapor fraction from a liquid fraction.
 8. Theprocess of claim 1, further comprising the step of flashing the effluentthrough at least one pressure drop to reduce the pressure of theeffluent by at least one-half of the pressure of the effluent in thehydroprocessing unit, prior to steam cracking the effluent in the steamcracker.
 9. The process of claim 8, wherein at least one of the at leastone pressure drops occurs substantially immediately prior to theseparator or within the separator.
 10. The process of claim 1, whereinthe effluent from the hydroprocessing unit has been subjected to thermalcracking in the hydroprocessing unit.
 11. The process of claim 1,wherein the effluent from the hydroprocessing unit is thermally crackedin the separator.
 12. The process of claim 11, wherein a majority byweight of the bottoms fraction comprises resid having a boiling point ofat least 900° F. (482° C.).
 13. The process of claim 1, wherein amajority by weight of the bottoms fraction comprises resid having aboiling point of at least 1050° F. (565° C.).
 14. The process of claim1, wherein step (iv) comprises passing the overhead from the separatorto a convection section of the steam cracker and then to a radiantsection of the steam cracker.
 15. The process of claim 1, furthercomprising the step of passing the hydroprocessed effluent to aconvection section of the steam cracker, then to the separator, andseparating the overhead stream from the bottoms in the separator. 16.The process of claim 15, wherein the step of separating includesseparating the effluent in a vapor liquid separation vessel, wherein thevessel is at least one of (i) heat integrated with the steam cracker,and (ii) heated with a heat source other than the steam cracker.
 17. Theprocess of claim 1, wherein the step of separating includes applyingheat to the separator.
 18. The process of claim 1, wherein the separatoris heat integrated with the steam cracker.
 19. The process of claim 1,wherein the effluent in the separator is heated to a temperature of atleast 750° F. (399° C.).
 20. The process of claim 1, wherein theeffluent in the separator is heated to a temperature of at least 800° F.(427° C.).
 21. The process of claim 1, wherein the effluent in theseparator is heated to a temperature of at least 850° F. (454° C.). 22.The process of claim 1, wherein the effluent in the separator is heatedto a temperature of from about 750° F. (399° C.) to about 900° F. (482°C.).
 23. The process of claim 1, wherein the effluent in the separatoris retained in the separator for at least a determined minimum amount oftime and not longer than a determined maximum amount of time.
 24. Theprocess of claim 1, wherein the effluent from the hydroprocessing unitcomprises hydroprocessed resid.
 25. The process of claim 1, furthercomprising the step of processing a resid-containing hydrocarbon feed inthe hydroprocessing unit, wherein the processing comprises combining thefeed with hydrogen at a temperature of from about 750° F. (399° C.) toabout 900° F. (482° C.).
 26. The process of claim 25, wherein theprocessing further comprises combining the feed with hydrogen at apressure of from about 1000 psig to about 4000 psig.
 27. The process ofclaim 1, wherein step (i) is further characterized by hydroprocessing afeed comprising crude or crude fraction containing greater than 30 wt %1050° F.+ resid, and greater than 30 wt % aromatics, and less than 15 wt% paraffins to obtain a hydroprocessed crude or hydroprocessed crudefraction, wherein the hydroprocessed or hydroprocessed crude fractioncomprises hydroprocessed resid.
 28. The process of claim 24, wherein thefeed comprises crude or resid-containing crude fraction containing atleast one impurity selected from: (a) sulfur in the amount of greaterthan 1 wt %, more preferably greater than 3 wt %, based on the weight ofthe feed; (b) resid in the amount of greater than 10 wt %, preferablygreater than 20 wt %, more preferably greater than 30 wt %, based on theweight of the feed; and (c) naphthenic acids as measured by a TAN of≧1.0, preferably ≧1.5, more preferably ≧2.0, still more preferably ≧2.5mg KOH/g oil, yet still more preferably ≧3.0 mg KOH/g oil (ASTM D-664).29. The process of claim 1, wherein the step of hydroprocessingsaturates at least 20 wt %, preferably at least 40 wt % of the aromaticspecies in the feed.
 30. The process of claim 1, wherein a bottomsproduct of step (iii) further comprises tar and wherein the tar isrecycled as a feed to the hydroprocessing unit.
 31. The process of claim1, wherein the feed to the hydroprocessing unit comprises steam crackertar.
 32. The process of claim 1, further comprising adding steam to atleast one of the effluent from the hydroprocessing unit and theseparator.
 33. The process of claim 1, further comprising the step ofseparating the steam cracker product comprising olefins to obtain anolefin product.
 34. A hydroprocessing and steam cracker system formaking olefins from a feed comprising at least one of crude and crudefractions comprising resid, the system comprising at least onehydroprocessor, at least one vapor liquid separator, and at least onesteam cracker.
 35. The system of claim 34, wherein the vapor liquidseparator is heat integrated with the steam cracker.
 36. The system ofclaim 35, wherein the vapor liquid separator comprises a visbreaker. 37.The system of claim 34, further comprising at least one steam crackerproduct separation and recovery apparatus to recover olefins from aneffluent from the steam cracker.
 38. The system of claim 34, furthercomprising a steam reformer that provides hydrogen to thehydroprocessing apparatus.
 39. The system of claim 34, wherein thesystem comprises in series and in the following order a hydroprocessor,a visbreaker, a steam cracker, and a steam cracker product separator torecover an olefin product.
 40. The system of claim 39, wherein thesystem further comprises a heater to heat the feed in at least one of(i) prior to the visbreaker, and (ii) in the visbreaker.
 41. The systemof claim 34, wherein the separator is heat integrated with the steamcracker.
 42. A process for making olefins from a hydrocarbon feedcomprising: (i) feeding a resid-containing hydrocarbon feed into ahydroprocessing unit; (ii) feeding hydrogen into the hydroprocessingunit and hydroprocessing the resid-containing hydrocarbon feed andhydrogen at a temperature of from about 750° F. (399° C.) to about 900°F. (482° C.) to create an incipient thermally cracked hydrogenatedeffluent; (iii) feeding an effluent from the hydroprocessing unit to avisbreaker and visbreaking the effluent at a temperature of up to 900°F. (482° C.); (iv) separating a vapor fraction and a bottoms fractionfrom the visbreaker, wherein a majority by weight of the bottomsfraction comprises resid having a boiling point of at least 1050° F.(565° C.); an (v) steam cracking the vapor fraction in a steam crackerto create a steam cracker effluent; and (v) separating the steam crackereffluent to recover at least one of a C2-C6 olefin and a single ringaromatic species.
 43. The process of claim 42, further comprising thestep of adding steam to at least one of the hydroprocessing uniteffluent, the overhead fraction, and the visbreaker, with steam.
 44. Theprocess of claim 42, wherein the step of heating comprises the step ofheating the hydroprocessing unit effluent at least one of prior tovisbreaking and during visbreaking.
 45. The process of claim 42, whereinthe step of heating comprises the step of heating the hydroprocessedresid during separation of the vapor fraction from the liquid fraction.46. The process of claim 42, wherein the step of heating comprises thestep of visbreaking the hydroprocessed resid to cause the separation ofthe vapor fraction from the liquid fraction.
 47. The process of claim42, wherein the step of heating comprises heating the hydroprocessedreside to a temperature of from about 750° F. (399° C.) to about 800° F.(427° C.).
 48. The process of claim 42, further comprising the step offeeding the bottoms fraction to another processing unit.
 49. The processof claim 42, wherein the visbreaker comprises a separation device and apressure reduction device, and wherein the visbreaker separates thevapor fraction from the liquid fraction after the effluent has passedthrough the pressure reduction device.
 50. The process of claim 42,wherein the separation device includes a separation vessel and thevessel includes a liquid volume that occupies at least one-half of thetotal volume of the separation vessel.